Photorefraction is a method for assessing the refractive error in a patient's vision, and is based upon a reflection of a flash source 10 from the retina 12. In FIG. 1, the light 15 from the flash source 10 propagates to the retina 12. In an eye that can accommodate or focus on the flash source 10, reflected light bundle 14 from the retina returns to the flash source 10 and does not enter the camera pupil 16 adjacent to the flash source 10. An image 18 of the eyes captured by the camera pupil 16 will appear dark or have a red eye pupil 20. A red eye pupil 20 is due to diffuse reflection (scattered light) of the flash source 10 within the eye of light-pigment retinas, so that the scattered light picks up the hue of blood vessels within the eye. Dark-pigmented retinas absorb the flash, and thus a dark eye pupil is imaged by the camera. If the eye cannot focus on a flash image plane 11 of the flash source 10 commonly due to a refractive error, then the specular reflected light 22 will be spread out, and some of the specular reflected light 22 will be collected by the camera pupil 16, as shown in FIG. 3. The specular reflected light 22 in an image 24 captured by the camera pupil 16 appears to form a yellow crescent 26 in the eye pupil 20, as shown in FIG. 4. The width of the crescent 26 is proportional to the residual refractive error of the patient's eye, which is not able to focus on the camera pupil 16. The width of the crescent 26 depends upon the 1) distance between the camera pupil 16 and the patient, 2) the separation of the flash source 10 to the camera pupil 16, 3) the diameter of patient's pupil 20, and 4) the patient's accommodative refractive error.